.\"	$OpenBSD: perror.3,v 1.10 2013/07/17 05:42:11 schwarze Exp $
.\"
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.\" the American National Standards Committee X3, on Information
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.Dd $Mdocdate: July 17 2013 $
.Dt PERROR 3
.Os
.Sh NAME
.Nm perror
.Nd write error messages to standard error
.Sh SYNOPSIS
.In stdio.h
.Ft void
.Fn perror "const char *string"
.Sh DESCRIPTION
The
.Fn perror
function looks up the language-dependent error message string affiliated
with an error number and writes it, followed by a new-line, to the
standard error stream.
.Pp
If the argument
.Fa string
is not the
.Dv NULL
pointer and is not zero length, it is prepended to the message string and
separated from it by a colon and a space
.Pq Ql \&:\ \& .
Otherwise, only the error message string is printed.
.Pp
The contents of the error message string are the same as those returned by
.Fn strerror
with argument
.Fa errno .
.Sh SEE ALSO
.Xr intro 2 ,
.Xr psignal 3 ,
.Xr setlocale 3 ,
.Xr strerror 3
.Sh STANDARDS
The
.Fn perror
function conforms to
.St -ansiC .
.Sh HISTORY
The
.Fn perror
function first appeared in
.At v4 .
